Memory devices are used in storage elements for many products, such as MP3 players, digital cameras, computer files, etc. As the application increases, the demand for the memory device focuses on small size and large memory capacity.
As such, it is desirable to develop a vertical channel memory to achieve greater storage capacity, a small size, and yet having excellent property and stability. However, a thin polysilicon is used as a channel layer in the vertical channel memory in general, which cannot avoid the contact landing risk and may bring an overlap issue because of the extra lithography process.